text: To a cold (–78°) stirred solution of lithium diisopropylamide (1.4–1.5 mmol/mmol of ketone) in dry THF (4 mL/mmol of base) under an atmosphere of argon was added slowly a solution of n-butyl-trans-2-vinylcyclopropyl ketone (1.19 mmol) in dry THF (1 mL/mmol of ketone), and the resulting solution was stirred at –78° for 45 minutes. A solution of freshly sublimed tert-butyldimethylsilyl chloride (1.6 mmol/mmol of ketone) in dry THF (1 mL/mmol of chloride) was added, followed by dry HMPA (0.5 mL/mmol of ketone). The solution was stirred at –78° for 15 minutes and at room temperature for 2–3 hours, and then it was partitioned between saturated aqueous sodium bicarbonate and pentane (10 mL and 20 mL/mmol of ketone, respectively). The aqueous phase was washed twice with pentane. The combined extract was washed four times with saturated aqueous sodium bicarbonate and twice with brine, and then dried (MgSO). Removal of the solvent, followed by bulb-to-bulb distillation of the remaining oil, gave the corresponding silyl enol ether as a colorless oil that exhibited no IR carbonyl stretching absorption. Thermolysis of the silyl enol ether was accomplished by heating (neat, argon atmosphere) at 230° (air-bath temperature) for 30–60 minutes. Direct distillation (140–150°/12 torr) of the resultant materials provided the cycloheptadiene in 85% yield: IR (film) 1660, 1260, 840 cm–1; 1H NMR (CDCl) δ 0.09 (s, 6H), 0.88 (s, 9H), 0.7–2.75 (m, 14H), 4.8 (t, 1H, J = 5.5 Hz), 5.5–5.9 (m, 2H).